Frangible fluid fittings and couplings are commonly employed in the fuel lines of aircraft. The purpose of such fittings is to minimize the escape of fuel during crashes, and such crash-worthy fittings and couplings are often employed to connect the several fuel tanks commonly used in aircraft of many types.
Crash-worthy fittings normally use a spring biasd self-closing valve which is held in the open position by a detent or stop which senses the presence of other fitting components. Upon the fitting being subjected to excessive forces, the fitting will fracture and portions thereof separate permitting the detent to be released that the valve may close.
A disadvantage with known crash-worthy fittings and couplings results from the typical construction wherein the detent is located at only one position on the fitting. Thus, as the direction of forces on the fitting and the nature of relative component movement cannot be predicted during a crash, it is possible that only partial separation of the fitting components may occur, and if such partial separation results at a location of the fitting as does not produce detent movement the valve will remain in the open position even though fluid is escaping through other portions of the fractured fitting. Conventional crash-worthy fittings can only insure 100% operation if the components sensed by the detent fully separate, which does not necessarily occur during each impact.
It is an object of the invention to provide a frangible fluid fitting which releases the self-closing valve upon the occurrence of minor fracturing and relative part movement, and regardless of the direction or location of the fracture with respect to the valve retaining detent.
Another object of the invention is to provide a crash-worthy fluid fitting which is of economical construction, yet is more dependable and sensitive in operation than prior crash-worthy fitting constructions.
An additional object of the invention is to provide a crash-worthy fuel intake fitting of the gravity type which permits fuel tanks to be filled to capacity.
An additional object of the invention is to provide a fuel tank fitting which permits tanks to be filled either by gravity or pressurized supply systems, and wherein the tanks may be filled to the maximum, and when using the pressurized supply, a flow control valve is automatically closed upon the tank filling.
In the practice of the invention two primary components of a fitting or coupling are interconnected by frangible means, such as pins, bolts, screws, weak cross sections, etc. The interconnection components may consist of the halves or primary parts of a coupling, or may consist of a fitting mounting plate attached to the tank and an inlet, port, extension or the like attached thereto. A self-closing valve is associated with one or both of the parts, and a detent retains the valve in an open position during normal operation.
At the surface at which the parts are interconnected an annular recess is defined in one part surrounding the flow passage. This recess is filled with hard balls, and the balls are retained within the recess by the attachment surface of the other part. The valve retaining detent engages the balls and is held in the valve open position thereby.
In the event of a crash or impact causing the frangible elements to fracture and permitting the fitting or coupling parts to even partially separate at the attachment surface, the balls are, at least, partially released from the recess, and are no longer sufficiently "compressed" to maintain the valve detent in the open position. The fitting valve closes sealing the fitting against fluid flow.
The use of the balls insures valve operation regardless of the direction of fracture or fitting part separation relative to the flow passage axis. Thus, even though only a single valve retaining detent is employed, the apparatus is sensitive to separation at the attachment surface at any location throughout the full 360.degree..
One of the crash-worthy fittings in accord with the invention is of the tank-filling type such as used with aircraft, and permits the fuel tank to be fully filled even though the filling port is located on the side of the tank below its uppermost regions. The fitting includes an extension extending even with the top of the tank, and the use of this extension simplifies refueling where a pressure system is not available, and permits maximum tank capacity.
An embodiment of the aforedescribed tank filling and extension fitting includes a port for alternatively permitting pressurized tank filling. The pressurized port includes a differential pressure-operated valve associated with venting means which closes the valve and terminates filling upon the tank capcity being reached.
In the practice of the invention a dependability is achieved for crash-worthy fittings and couplings not heretofore possible, and the objects of the invention have been attained by the inventive concepts.